Error on adding service refrerence to DNN site

have successfully created a working model interacting with an external web service via a service reference in my Visual Studio dev environment.

I now want to set this up on our Evoq Content Basic site as a DNN module. So Step 1 was to add the service reference to dnn, but as soon as the reference was created in the app_webreference folder it brings down our site with the following error below.

Reference.svcmap: Could not load file or assembly 'antlr.runtime, >Version=2.7.6.2, Culture=neutral, PublicKeyToken=1790ba318ebc5d56' or one of >its dependencies. The system cannot find the file specified. Assembly Load Trace: The following information can be helpful to determine >why the assembly 'antlr.runtime, Version=2.7.6.2, Culture=neutral, >PublicKeyToken=1790ba318ebc5d56' could not be loaded. WRN: Assembly binding logging is turned OFF. To enable assembly bind failure logging, set the registry value >[HKLM\Software\Microsoft\Fusion!EnableLog] (DWORD) to 1. Note: There is some performance penalty associated with assembly bind failure logging. To turn this feature off, remove the registry value >[HKLM\Software\Microsoft\Fusion!EnableLog].

I have never added a web service in DNN before so I am hoping the error will mean something to one of you guys. after all, it should not be that hard? and adding a service reference is the method most DNN tutorials recommend